Digester



Dec. 25, 1962 J. R. STARRETT DGESTER Filed Nov. 150, 1959 Unite Fico 3,076,156 DIGESTER James R. Starrett, Springfield, Ohio, assigner to The Bauer Bros. Co., Springfield, hio, a corporation of Ohio Filed Nov. sa, 1959, ser. No. 856,212 8 Claims. (Cl. 162-237) This invention relates to continuous treatment digesters of the moving conveyer type, and particularly to a new and improved form of such `digester providing for circulation of the treating iiuids relatively to conveyer carried fibrous Vor like material.

Digesters of the class described comprise a shell or vessel holding a quantity of a cooking liquor, land within the shell, provide conveyer means to carry fragmentary or librous material Ithrough the liquor bath in order that it may be impregnated and softened thereby as a preliminary to a debering of the material. The invention has particular, although not limited, reference to a type of digester in which the vessel takes the form of a tubular shell interior partitioned to provide upper and lower passages which are traversed by the conveyor means, the vessel `being disposed in yan inclined -attitude and provided with gravity acting means for admitting and discharging from the upper and lower passages, respectively, the material for treatment.

The object of the invention is to simplify the construction as well as the means and mode of operation of digesters, whereby such digesters may not only be economically manufactured, but will be more efficient, flexible, and satisfactory in use, adaptable to a wide variety of applications, and be unlikely to get out of order.

A further object of the invention is to achieve la circulating movement of a treating fluid through the whole or a selected segment of the path traversed by the conveyer means.

Another object of the invention is to provide for circulating iiuid flow as described in a plurality of individual zones, each corresponding to a segment of the path traveled by the conveyer means and ,each operating independently of the other to the end that fluids may be circulated in different zones differently characterized as to temperature or chemical concentration or both.

A further object of the invention is to provide means for circulating fluids in different directions, in dilerent zones.

A further object of the invention is to exercise a control over a changing condition of the circulating iluid or fluids in order that their temperature or chemical concentration and the like may be maintained at predetermined levels or changed at will.

Still another object of the invention is to provide a digester of the kind described generally new in its concept of and means for fluid circulation and utilizing a hollow divider as a partitioning means within the shell to dene inlet and outlet chambers having a screened communication with the shell interior.

A further object of the invention is to provide a digester possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the -above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

FIG. 1 is a view in longitudinal section, and partly diagrammatic, of a continuous treatment digester in accordance with the illustrated embodiment of the invention and `showing circulating systems for the treating fluid;

FG. 2 is a detail view fragmentary in `form and taken substantially alonY the line 2 2 of FIG. l, and being enlarged with respect to FIG. l; and

FIG. 3 is a detail view in longitudinal section, fragmentary in form, of the central partition means in the shell, showing the inlet and outlet chambers therein for the circulating treating liuid, and being also enlarged with respect to FIG. 1.

Like parts are indicated by similar characters of reference throughout the several views.

in its illustrative embodiment, the invention is disclosed in a digester of the moving conveyer type in which the vessel holding the cooking liquor or vapors or both has a generally cylindrical tube like shape and is installed on end `but inclined from the vertical to an extent of approximately 45. In FIG. l, the digester is shown in a horizontal position as a matter of convenience of illustration. Thus, and as shown, a tubular shell 1li is closed at what may be considered its upper end by a cap 11 and closed at what may be considered its lower end by a cap 12. Near the upper end of the tube shell is an inlet fitting 13 admitting under control of a valve or other metering device 14 fibrous or other fragmentary material to the interior of the shell. Also in the upper end of the tube shell 1t?, and approximately diametrically opposed to the inlet 13 is an outlet iitting 15 by way of which `treated material leaves the digester. A longitudinally extending partition 1o separates the inlet and outlet littings 13 and 15 and serves in .ei-lect to divide the shell interior into upper and lower liow passages 17 and 18. A quantity of chemical liquor is contained in the shell,

the normal level thereof being below the fittings 13 and 1S, for example at a point indicated by the line 19.

Movement of the fibrous or fragmentary material through the shell, or more particularly through the passages 17 and 18, is accomplished by a moving conveyer means including a continuous chain 21 on which are mounted paddle-like iiights 22. The liights 22 extend angularly from the chain 21 and are longitudinally spaced apart to receive and propel through the shell the fibrous material admitted through fitting 13. The chain 21 encompasses `the partition 16, in an endwise direction, and at its one end has a driven engagement with a sprocket wheel 23 on a transverse shaft 24 suitably driven in a rotary sense from outside the digester. At its opposite end the chain 21 extends over a rotary guide disc 25 mounted on a transverse shaft 26 and forming a part of a closure unit 27 urged `by a tensioning device 23 downwardly or outwardly in the shell 1t) in a manner to tension the chain 21. The closure unit 2.7 includes a hemispherical part 29 having its concave surface facing inwardly in the shell in a manner to provide an arcuate passage 31 at the bottom of the shell interconnecting the How passages 17 and 18 and providing a space for free movement of the liights 22 from one passage to the other. A guide rail 32 is mounted on one side of the partition 16 to project upward into the passage 17 where its upper edge is in guiding and supporting relation to the chain 21.

The movement of the material for treatment from the iitting 13 to the fitting 15 accordingly is by way of a circuitous path which takes the material beneath the level of contained chemical liquids to the bottom of the vessel and then returns it to and above the liquid surface for discharge at litting 15. The angle of inclination at which the digester is installed provides for gravity movement of the material into and out of the vessel and it will, of course, be understood that the movement of the material into and out of the shell is controlled with reference to the speed of movement of the conveyor means so that the material assumes within the shell a loosely packed form Which does not inhibit a free ow of liquid through the material for uniform exposure of the individual fragments to the action of the liquid. Entrance of the fibrous material to the digester is, as noted, under control of a continuously operating rotary valve ld. A similar valve 33 controls flow out of the fitting l5, both valves precluding pressure loss from the shell.

The instant invention contemplates the introduction, in a digester characterized as the foregoing, of a principle of fluid circulation in which the fluids for treatment of the material are circulated within the shell relatively to the moving material. While this may be accomplished through suitable connections made directly to the wall of the shell, along with external piping, according to a feature of the instant invention at least scme of the fluid circulation is by Way of inlet and outlet chambers in the partition lo. Thus, this element is constructed as a hollow, rectangular beam which at its longitudinal side edges is welded or otherwise secured to the inner face of the shell 10. The ends of the partition, as seen, terminate short of the ends of the shell and are encircled by the conveyer chain 2l. The partition f6 accordingly presents upper and lower surfaces 3d and 3S which, in width, correspond approximately to the internal diameter of the shell respectively facing upper iiow path ll7 and lower flow path 13. The walls dividing such surfaces are held apart by spacers 36. length of the partition these spacers are used to define the ends of transverse recesses in the partition formed by cutting away the surface 34 or the surface 35 between an adjacent pair of spacers. Thus, there is formed in the surface 3d in this manner recesses 37, 3S and 39. In similar manner there are formed in the surface 35 recesses el and 4Z, circulation through the lower flow pass I8 further being by way of a fitting d3 installed in the wall of the shell l0. The several recesses 357-42 serve selectively as inlet and outlet chambers for the circulating fluid or uids and to this end have individual connections 44 at their ends to the exterior of the shell l0. Further, and as shown in FIG. 3, there is installed in each recess 37-42 a rectangular hollow screen 45 which provides for free fluid communication of the Connection i4 with the interior of the shell while prevening a clogging of such connection by the fibrous material within the shell.

The inlet and outlet chambers of the partition 16 are selectively interconnected for fluid circulation. Thus, chamber 33 serves as an outlet, a fluid being drawn therefrom to the exterior of the shell by way of a line 46 in which is interposed a pump 47. lThe line 46 leads back to the shell, more particularly to chamber 37 therein, so that under the influence of the pump 47 fluids drawn from outlet chamber 33 are circulated back to the vessel at chamber 37. There they are allowed to escape through the screen 45 into the pass 17 of the shell interior Where they follow a path indicated by the group of arrows 43 to outlet chamber 3S for recirculation as described. There may further be interposed in the line 46 means to treat or to control a changing condition of the circulating `fluid such as the temperature thereoiC or the chemical concentration. In the illustrated instance, as indicated, the fluid is directed through a heat exchanger 49 so that the circulating fluid may have its temperature changed by being placed in heat transfer relation to another fluid of different temperature circulating through the heat exchanger in another circuit. In another segment of the flow path through the digester the chamber 39 serves as an inlet chamber, flow therefrom following the path indicated by the group of arrows i9 to the lower end of the shell through arcuate passage 31 and into the lower end of flow passage l, this segmental path terminating in chamber lil which serves as an outlet chamber. Circulation from chamber di to chamber At selected locations along the 5 39 is by way of an external connection 5l in which is a pump 52 and which also incorporates means for controlling a changing condition of the fluid as for example a heat exchanger 53. The chamber 42 serves as an outlet chamber. Fluid is drawn therefrom through a line 54S., passes through a heat exchanger 55 and a pump 56 and returns to the shell by way of opening 43 in the side of the shell. This flow, internally of the shell, follows the route indicated by the group of arrows 57 back to chamber' 42.

The selection of the and outlet connections has the effect of defining individual zones of fluid movement. Any number of suoli Zones may be used. Each may circulate a nt volume of fluid, and each may circulate the same or different volumes of fluid at different temperatures and chemical concentrations. The Zones may independently `circulate dinerent chemical solutions. Eacr circuit removes iiuid from its own zone, changes its te nuerature or chemical concentration or both and returns it to the shell. Since the purpose of the fluid is to surround and treat the material being conveyed the fluid advantageously passes through the mass of the material rather than around it. Accordingly the flow is directed through the bottom of the mass in each segment. lt is contemplated that all fluid flows shall be constant. Cirg Zone lengths may be increased by shutting off and discharge connections at selected chambers, thus directing the iiow of one Zone through the adjacent zone and, of course, the entire flow pass through the shell may be made a single fluid circulating circuit. The outlet chambers in the circulating fluid system are located beneath the liquid level i9 as are the fluid inlets in the illustrated instance although these may be located any- `vhere along the length of the partition i6.

Under certain conditions of operation it may be desirable to introduce thc first fluid in to the chamber above the level of the incoming material and also above the liquid level t9. In this form, the initial chamber 37 is located above the entrance l?, as shown for example at 37', FiG. l. With this type of construction the uid is sprayed upon the incoming material as it enters the chamber through the inlet f3 prior to the submersion of the material in the liquid.

It is also desirable for some types of operation that the liquid level i9 raised Within the vessel 1t) and such level can be located at any desired point either above o1' below that shown.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle :Involved or sacrificing any of its advantages.

While in order to comply with the statute the invention ias been described in language more or less specificv as to structural features, it is to be understood that the invention is not limited to the specic features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A continuous treatment digester of the moving conveyer type having a shell and partition means dividing the shell into segments successively traversed by material under treatment; characterized by means defining inlet and outlet chambers in said partition means, and means for circulating fluids through said shell between said chambers.

2. A continuous treatment digester of the moving conveyer type having a shell and partition means dividing the shell into segments successively traversed by material under treatment; characterized by means defining inlet and outlet chambers in said partition means, and a plurality of means circulating individual fluids through different segments of said shell between said chambers of said partition means.

3. A continuous treatment digester of the moving conveyer type having a shell and partition means dividing the shell into segments successively traversed by material under treatment; characterized by means for circulating Huid through said shell including passages formed at least in part by chambers in said partition means.

4. A continuous treatment digester of the moving conveyer type, including a shell holding a quantity of cooking liquor, shell being used in an upwardly extending position inclined from the vertical and having an inlet for `fibrous material above the normal liquid level, the said cooking liquor forming under gravity influence a single body or contained liquid in the shell, conveyer means movable through said shell to conduct the librous material in a loosely packed form into and out of the contained cooking liquor, and means for circulating uids of different characteristics through zones in said shell, said zones having inlet and outlet ends both of which are beneath the level of cooking liquor, said zones being defined by selected boundaries Within .the contained body of cooking liquor.

5. A continuous treatment digester of the moving conveyer type including a shell, said shell being used in an upwardly extending position inclined from the vertical and holding a quantity of cooking liquor, said liquor forming under gravity influence a single body of contained liquid in said shell, unidirectional conveyer means movable in a path through said shell to conduct brous material in a loosely packed form in to and out of the contained body of cooking liquor, means dening a plurality of uid ovv zones in said shell, including a fluid inlet and a fluid outlet for each zone, each of said zones being coincident with a segment of the path of said conveyer means through the shell, and means independently circulating a iluid through each of said zones, the said inlet and outlet of each zone being so arranged that fluid flow through said zone is in the same direction as the movement of said conveyer means, said flow zones being located to be within the said body of contained liquid.

6. A continuous treatment digester of the moving conveyor type, including a tubular shell, a partition extending longitudinally in said shell, said shell having inlet and outlet opening for a fibrous material for treatment, continuous conveyer means arranged longitudinally in said shell and taking a path over the ends of said partition, said conveyer means conducting the .fibrous material from said inlet to said outlet through said shell in continuous moving fashion, fluid chambers in said partition having a screened communication with the interior of said shell and connected to the exterior thereof, a fluid flow system using certain of said chambers as inlets to said shell and certain others as outlets therefrom, the fluid from an inlet chamber through a portion of the shell interior in contact with the brous material therein to an outlet chamber, and means for circulating the fluid from an outlet to a selected inlet, said outlet and said selected inlet comprising a zone corresponding to a segment of the path of said conveyer means through which a fluid may be circulated substantially to the exclusion of the remainder of the shell interior.

7. A continuous treatment digester according to claim 6, characterized by a plurality of huid circulating means supplying fluids of different characteristics to different zones corresponding to respective segments of the path of said conveyer means.

8. A continuous treatment digester according to claim 6, characterized by a plurality of fluid circulating means supplying fluids of different characteristics to different zones corresponding to respective segments of the path of said conveyor means, and further characterized in thatL said shell holds a quantity of treating liquor, said zones of circulating fluid al1 being located beneath the level of said liquid.

References Cited in the tile of this patent UNITED STATES PATENTS 891,300 Smyth lune 23, 1908 1,186,655 Freeman June 13, 1916 1,679,336 Dunbar July 31, 1928 1,938,802 Braun Dec. 12, 1933 2,200,034 Merrill May 7, 1940 2,425,335 Messing et al Aug. 12, 1947 2,966,215 Durkee Dec. 27, 1960 2,969,113 Green Jan. 24, 1961 FOREIGN PATENTS 333,426 Great Britain Aug. 14, 193i) 

